Microfluidic devices have become increasingly popular due to their ability to analyze minute quantities of samples and their high-throughput sampling capabilities. Novel, versatile, and robust fabrication methods are needed both to make microfluidic devices more available to the research lab and the commercial market. In microfabrication, rapid prototyping capability is highly desirable since design modification can be done quickly and inexpensively.
There are many fabrication techniques available in creating microchips for use in microfluidic devices, such as photolithography with poly(dimethylsiloxane) PDMS, micromachining, thermal embossing, and injection molding, each technique having its own challenges in each step of fabrication. There are many parameters that need to be considered and optimized before a good fabrication technique can be realized. One of the most commonly used methods for fabrication, such as making microchannels, is hot embossing as it allows for a simple and quick means to make replicas of a master template. The next step after creating the microchannel is the bonding process to form a complete fluidic channel. Many bonding procedures have been used, such as solvent bonding, thermal bonding, and microwave bonding, each with its own advantages and drawbacks, but all having the same principle, which is to provide a quick and effective bonding method that allow for channel preservation.
A microfluidic system usually requires multiple interconnects, and currently there are no standard interconnections used in this field. A simple and reliable interconnect is highly desirable for microfluidic devices, especially for rapid prototyping. There are a number of current products available to accommodate these needs. The most common and simplest approach is the direct integration of tubing to the ports of the microchip using epoxy glue or adhesives. However, direct connection to the inlet reservoir using an epoxy often leads to occluded microchannels. Commercially available connections, such as NanoPort™ from IDEX use a threaded nut and ferrule system, and can be integrated onto the chip ports by means of adhesive rings and epoxy glue. The drawback to this method is that the non-removable epoxy glue takes time to cure and requires high temperatures for complete curing, making it incompatible with low glass transition (Tg) polymers. Other available products, such as edge connectors provide efficient interfacing and allow rapid connections and reusability. However, they are designed to be interfaced to a standard microchip format. This limits the compatibility of other chips with different geometries, layout or sizes. As a result, a need exists in this field for connecting components of microfluidic devices in an effective, efficient, and versatile manner.
Conventional surface modification processes concerning coupling biological compatible polymers with biomolecules can often be time consuming and labor intensive. For example, standard functionalization procedures of biomolecules typically involves the following steps: 1) activating the surface; 2) applying respective reactive groups and linkers to the surface of the substrate of interest; 3) incubating the sample (typically requiring 2 to 12 hours, depending on the type of molecules); 4) washing away the excess unreacted molecules; 5) applying biomolecules of interest; and 6) rinsing. There exists a need in this field for a more efficient, cost-effective approach.